The present invention relates to a dryer apparatus for paper, cardboard or some other porous fiber web. The invention replaces the pressurized-steam heated cast-iron dryer cylinders available since the nineteenth century.
Development in the art of paper making machines has been slow and concentrated mainly on the so-called wet end. An object of the machine is to dewater pulp pumped onto the machine and formed into an even fiber web. As for a newsprint machine, for example, the dewatering breaks up as follows:
the wire section 98.8%, by suction and gravitation PA0 the press section 0.6%, by pressing PA0 the dryer section 0.6%, by steam-heated cylinders.
The dryer section constitutes about 80% of the total machine weight and also represents technology from decades ago.
The dryer section of a paper machine, e.g. in the production of cardboard and newsprint, comprises 45-65 cast-iron cylinders, diameter 1.5-1.8 meters, fast rotating (peripheral speed 700-2000 meters/min.) pressure vessels. Carrying a fragile fiber web through such a complicated installation without breaking the same and as required by quality standards is one of the most demanding challenges in paper making. The dryer section also sets strict requirements for the building and subconstructions. Other factors adding to complexity include the passage of a paper web, drive, machine ventilation, pocket ventilation, steam and condensate system, dryer felts, etc.
The "Yankee" cylinder is used for the manufacture of one side glazed (MG-) papers as well as cardboard and creped papers (tissue and industrial crepes). It is a highly massive and demanding body of casting, having a diameter of 3-6 meters, a cylinder length of 3-6 meters, and a weight of 50-100 tons with accessories. Heretofore, there has been no viable, more preferred option available.